One aim of this research is to elucidate principles of nucleic acid conformation and interactions by studying fragments of polynucleotides alone and complexed with other molecules. Utilizing the methods of x-ray crystallography we shall determine the structures of oligonucleotides complexed with frameshift mutagens such as proflavine, antimalarials such as quinacrine, and antibiotics such as nitropsin. These studies should also provide a basis of understanding of the mechanisms of drug action and mutagenesis. In an attempt to understand how enzymes interacton with nucleic acids and/or the constituents, we shall initiate studies on an allosteric enzyme, AMP nucleosidase, which catalyzers the cleavage of the glycasidic bond in AMP.